1. Field of the Invention
The presently disclosed invention relates to tools for removing threaded fasteners and, more particularly, fasteners wherein the perimeter surface of the fastener has been damaged by corrosion or mechanical stress such that the corners of the polygonal surface have become rounded.
2. Description of the Prior Art
Many types of threaded fasteners are known in the prior art. Such fasteners have various designs for cooperation of the fastener with a threaded member. Some of these fasteners, such as wing nuts or thumb screws, are intended to be applied and removed without the use of tools. Other fasteners, such a threaded nuts, require the use of tools for their application and removal.
In particular, many types of fasteners have an inner threaded surface and an outer polygonal surface, typically a hexagonal surface. The inner threaded surface cooperates with the threaded member and the outer surface cooperates with a tool that is used to apply or remove the fastener from the threaded member. Various types of tools have been developed and used for this purpose. Examples are shown and described in U.S. Pat. Nos. 4,328,720; 4,671,141; and 4,993,289. Basically, these tools cooperate with the polygonal sides of the fastener to transfer a torque force that is required to turn the fastener on and off of the bolt or other threaded member.
There has been a persistent problem with the polygonal-style threaded fasteners in the prior art when the polygonal sides become worn or damaged the sides no longer define the requisite shape that is necessary for the fastener to cooperate with the tool that is designed for its application and removal. Frequently this problem arises when the fastener is to be removed and the polygonal sides have been damaged due to corrosion or mechanical wear. In this situation, the conventional tools that are designed for the removal of the fastener are no longer operative. Generally, the conventional tool will merely slip over the rounded or damaged corners between the polygonal sides of the fastener so that the tool will not remove the fastener.
This difficulty has been recognized in the prior art wherein different types of tools have been developed for the removal of damaged polygonal fasteners from their threaded members. Examples of such tools are shown and described in U.S. Pat. Nos. 3,996,819 and 5,551,320. U.S. Pat. No. 3,996,819 is directed to a wrench socket wherein a number of raised teeth are arranged in a conical-shaped opening in the tool. The teeth are aligned angularly within the conical opening. As the tool is turned to remove the fastener, the teeth engage the fastener and cause the tool to transfer torque to the fastener so that it can be removed. U.S. Pat. No. 5,551,320 is directed to an improved tool for removing damaged fasteners. In this tool, a plurality of teeth also engage the fastener for the purpose of removing the damaged fastener from the threaded member.
One difficulty with the tools for removing damaged fasteners as known in the prior art was that the tools could not be readily manufactured in accordance with conventional manufacturing processes. Machining the individual teeth into a tool body such as described in U.S. Pat. Nos. 3,996,819 and 5,551,320 was not practical on a commercial scale. Broaching the teeth into the tool body was also found to be unworkable because the geometry of the tool caused the broach to seize in the tool. This resulted in the destruction of either the broach or the tool, or both.
Accordingly, there was a need in the prior art for a commercial manufacturing method that could be practiced to manufacture tools for removing damaged threaded fasteners.
In accordance with the invention, a cold metal forming process for making a tool to remove damaged fasteners is disclosed herein. According to the process, the tool is cold formed from a tubular section that has a cylindrical inside surface and a tapered outside surface. In the cold forming process, the tubular section is driven onto a floating punch that has helical splines at the working end of the punch. The floating punch has a substantially constant radius and is secured in the longitudinal dimension with respect to the die plate, but is freely rotatable in the angular direction. As the tubular section is driven onto the punch, the punch angularly rotates in response to the longitudinal movement of the tubular section and in accordance with the pitch of the helical splines. The tubular section rotates in a first direction in accordance with the direction of the splines on the punch to form helical splines at one end of the inside surface of the tubular section.
After the splines are formed in the inside surface of the tubular section, the tubular section is stripped off of the end of the floating punch. As the tubular section is stripped off the end of the floating punch, the punch angularly rotates in the direction that is opposite from the first angular direction. In this way, the tubular section is removed from the floating punch while preserving the helical splines on the inner surface of the tubular section.
After the tubular section is stripped off of the floating punch, it is extruded through a round-to-polygonal extrusion die insert. This step cold forms the tapered outer surface of the tubular section to a polygonal surface that has a constant cross-section. The same step also cold forms the inside surface of the tubular section from a cylindrical inner surface to a surface that is tapered and polygonal at the one end of the tubular section having the internal splines. The direction of the taper of the inner surface provides the largest cross-section at the end of the tubular section that was driven onto the floating punch.
Also preferably, the step of driving the floating punch into one end of the tubular section includes the steps of positioning the tubular insert in a die that is slidably located in a die sleeve. One end of the tubular section is then contacted to move the tubular section toward the floating punch and then drive a portion of the tubular section over the splined end of the floating punch. A cylindrical kickout sleeve that is concentrically located around the floating punch and is longitudinally slidable with respect to the. floating punch is then extended to contact the end of the tubular section and strip the tubular section off of the floating punch.
More preferably, it has been found that the tool made in accordance with the disclosed method includes a first end and a second end that is oppositely disposed on the tool body from the first end. The tool has an outside surface that is defined between the first and the second ends. In addition, the tool has an inside surface that defines a closed passageway between the first and second ends. A portion of the inside surface that is adjacent to the second end is a polygonal surface that defines a central opening with the area of the central opening decreasing as the longitudinal position away from the second end increases. The portion of the inside surface that is adjacent to the second end also includes a plurality of spiral splines that extend radially inward.
Also preferably, the sides of the polygonal internal surface of the tool are joined by corners and the polygonal sides have midpoints that are located midway between the respective corners. At the second end of the tool, the radial inward extent of the splines is increases as the angular location of the spline is closer to the angular location of the midpoint of the polygonal side on which the spline is located.
Most preferably, the spline is defined by roots on opposite side of a crest. The depth of the spline is the difference between the radial position of the root and the radial position of the crest, the depth of the spline being substantially constant. Also, at a given longitudinal position along the splines, the crest of the spline cooperates with each of the roots to define adjoining sides of the spline. The bisector of the internally included angle between the sides defines the relief angle of the spline at a given longitudinal position, the relief angle of the spline decreasingly in the longitudinal direction away from the second end of the tool.
Other features, objects and advantages of the disclosed invention will become apparent to those skilled in the art as a presently preferred embodiment of the disclosed tool and a presently preferred method of making the same proceeds.